* Trivia: guess what jmde (JMDE) stands for?
..and to think, back when we used VSS we didn't even have commit messages! Soon after, "AudioChannel" became instantiable and went on to be known as "MediaTrack", and as one would hope many other things ended up changing.

Wow, 9 years have gone by.

I've been having a blast this week working on something that let me make this:

The interesting bit of this is not the contents of the video itself -- 3 hasty first-takes with drums, bass, and guitar, each with 2 cameras (a Canon 6D and a Contour Roam 2) -- but how it was put together.

I've spent much of the last week experimenting with improving the video features of REAPER, specifically adding support for fades and video processing. This is a ridiculously large can of worms to open, so I'm keeping it mostly contained in my office and studio.

Working on video features is reminding me of when I was first starting work on what would become REAPER: I was focused on doing things that I could use then and there for things I wanted to make. It is incredibly satisfying to work this way. So now, I'm doing it in a branch (thank you git), as it is useful for me, but so incredibly far from the usability standard that REAPER represents now (even if you argue that REAPER is poorly designed, it's still 100x better than what I've done this week). You can't go put half-baked, poor performing, completely-programmer-oriented video features into a 9 year old program.

Here is a .gif showing how the video filters work -- the syntax has since been simplified a bit, but basically you have meta-video items which can combine other video items on the fly. So you can write new transitions or customize existing transitions while you work (which is something I love about JSFX).

I'm going to keep working on this, it might get there someday. Former Vegas fans, fear not, REAPER isn't going to become a video editor. I'm just going for a taste...

I just posted (to our prerelease site) LICEcap 1.25 beta 3, which includes support for using transparency for smaller images. I had some fun debugging this (including some very stupid mistakes on my part that took about an entire day to debug, oops).

I also had some fun writing logic to decide what to do when a pixel could be encoded as transparent, but also could be well-represented by an indexed color. Iniitially I had it only use the indexed value if the previous pixel was indexed, but it ended up being quite a bit better to do track the occurence of transparent pixels and pixels of that index, and use the one that is more common. There is probably a better algorithm to use here, but that saw some good gains.
For comparison, I ran 1.24 and 1.25 beta 3 at the same time for a stupid demo video. The 1.24 version was 2.5MB, the 1.25 beta 3 version was 1.5MB. WIN. It ultimately is highly dependent on the content, though, so I might look at trying some other things out...

Very often in computer code integers are divided by powers of two, such as 2, 4, 8, 16, 32, 64, and so on). These divisions are much faster than dividing by other numbers (since computers represent the underlying number in binary). In C/C++, there are two ways this type of division is typically expressed: normal division (x/256), or a shift (x<<8). These two methods produce the same results for non-negative values, and depending on the meaning of the code in question, (x/256) is often more readable, and thus I use it regularly.

If x is signed and is negative, division rounds towards 0, whereas the shift rounds towards negative infinity, but in situations where rounding of negative values is not important, I had generally assumed that modern compilers would generate similarly efficient code (reducing x/256 into a single x86 sar instruction).

It turns out, testing with a two modern compilers (and one slightly out of date compiler), this is not the case.

Ideally, a compiler should generate identical code for each of these functions. In the case of the loop counter, if v is less than 0, how it is rounded makes no difference. In the case of the parameter to b(), the code v >> 16 is only evaluated if v is known to be above 0.

Let's look at the output of some compilers (removing decoration and unrelated code). I've marked some code as bold to signify instructions that could be eliminated (with slight changes to the surrounding instructions):

In the first function (division), the LLVM optimizer appears to have removed the ternary expression (checking to see if v was greater than 0), likely because it knew that if the loop was running, v was greater than 0. Unfortunately, it didn't apply this knowledge to the integer divisions of v, which would have allowed it to not generate (substantial) rounding code.

In the second function (shifts), LLVM wasn't required to generate rounding code (as C's >> maps to x86 sar directly), but it also didn't use the knowledge that v would be greater than 0.

VS 2013 generates different rounding code for the division, using cdq/movzx (or cdq/and if shifting by something other than 8 or 16 bits).

Also worth noting is that VS 2013 doesn't even bother moving the invariant ternary operator and (v/65536) or (v>>16) out of the loop. Ideally, it could move that calculation out of the loop, or remove the ternary operator completely. Ouch. I have to say, VS 2013 does seem to produce pretty good code overall, but I guess most of ours is heavily in floating point these days.

gcc 4.4 does an interesting job, using lea to generate v+255, and then cmovns to replace it with v if v is non-negative. It doesn't bother generating rounding code for v/65536, but it does still generate rounding code for v/256, even though any non-positive result for v/256 is treated the same way throughout. Also, gcc doesn't eliminate the non-varying ternary expression, nor put the constant v/65536 or v>>16 outside of the loop.

Conclusions?

I'm not sure what to say here -- modern compilers can generate a lot of really good code, especially looking at floating point and SSE, but this makes me feel as though some of the basics have been neglected. If I were a better programmer I'd go dig into LLVM and GCC and submit patches.

I should have also tested ICC, but I've spent enough time on this, and the only ICC version we use is old enough that I would just regret not using the latest.

For comparison, here is what I would like to see LLVM generate for f():

Performance-wise, I'm sure they wouldn't differ in any meaningful way, but the decrease in size would be nice.

Finally: write for the compiler you have, not the compiler you wish you had. When performance is important, use shifts instead of divides, or use unsigned types (which really should generate the same code for (x/256) vs (x>>8)). Move as much logic out of the loop as you can -- yes, the compiler might be able to do it for you, but why depend on that? But most important of all: test your assumptions.

I've been investigating, once again, the performance of drawing code-rendered RGBA bitmaps to NSViews in OSX. I found that on my Retina Macbook Pro (when the application was not in low-resolution legacy mode), calling CGContextSetInterpolationQuality with kCGInterpolationNone would cause CGContextDrawImage() to be more than twice as fast (with less filtering of the image, which was a fair tradeoff and often desired).

The above performance gain aside, I am still not satisfied with the bitmap drawing performance on recent OSX versions, which has led me to benchmark SWELL's blitting code. My test uses the LICE test application, with a screen full of lines, an opaque NSView, and 720x500 resolution.

OSX 10.6 vs 10.8 on a C2D iMac

My (C2D 2.93GHz) iMac running 10.6 easily runs the benchmark at close to 60 FPS, using about 45% of one core, with the BitBlt() call typically taking 1ms for each frame.

Here is a profile -- note that CGContextDrawImage() accounts for a modest 3.9% of the total CPU use:

It might be possible to reduce the work required by changing our bitmap representation from ABGR to RGBA (avoiding sseCGSConvertXXXX8888TransposeMask and performing a memcpy() instead), but in my opinion 1ms for a good sized blit (and less than 4% of total CPU time for this demo) is totally acceptable.

I then rebooted the C2D iMac into OSX 10.8 (Mountain Lion) for a similar test.

Running the same benchmark on the same hardware in Mountain Lion, we see that each call to BitBlt() takes over 6ms, the application struggles to exceed 57 FPS, and the CPU usage is much higher, at about 73% of a core.

Here is the time sampling of the CGContextDrawImage() -- in this case it accounts for 36% of the total CPU use!

Looking at the difference between these functions, it is obvious where most of the additional processing takes place -- within img_colormatch_read and CGColorTransformConvertData, where it apparently applies color matching transformations.

I'm happy that Apple cares about color matching, but to force it on (without allowing developers control over it) is wasteful. I'd much rather have the ability transform the colors before rendering, and be able to quickly blit to screen, than to have to have every single pixel pushed to the screen color transformed. There may be some magical way to pass the right colorspace value to CGCreateImage() to bypass this, but I have not found it yet (and I have spent a great deal of time looking, and trying things like querying the monitor's colorspace).

That's what OpenGL is for!
But wait, you say -- the preferred way to quickly draw to screen is OpenGL.

Updating a complex project to use OpenGL would be a lot of work, but for this test project I did implement a very naive OpenGL blit, which enabled an OpenGL context for the view and created a texture for drawing each frame, more or less like:

This resulted in better performance on OSX 10.8, each BitBlt() taking about 3ms, framerate increasing to 58, and the CPU use going down to about 50% of a core. It's an improvement over CoreGraphics, but still not as fast as CoreGraphics on 10.6.

The memory use when using OpenGL blitting increased by about 10MB, which may not sound like much, but if you are drawing to many views, the RAM use would potentially increase with each view.

I also tested the OpenGL implementation on 10.6, but it was significantly slower than CoreGraphics: 3ms per frame, nearly 60 FPS but CPU use was 60% of a core, so if you do ever implement OpenGL blitting, you will probably want to disable it for 10.6 and earlier.

Core 2 Duo?! That's ancient, get a new computer!
After testing on the C2D, I moved back to my modern quad-core i7 Retina Macbook Pro running 10.9 (Mavericks) and did some similar tests.

Normal: 12-14ms per frame, 46 FPS, 70% of a core CPU use

Normal, in "Low Resolution" mode: 6-7ms per frame, 58FPS, 60% of a core CPU use

Normal, without the kCGInterpolationNone: 29ms per frame, 29 FPS, 70% of a core CPU use

Normal, in "Low Resolution" mode, without kCGInterpolationNone: same as with kCGInterpolationNone.

Interestingly, "Low Resolution" mode is faster in all modes except for GL, where apparently it is slower (I'm guessing because the hardware accelerates the GL scaling, whereas "Low Resolution" mode puts it through a software-scaler at the end.

Let's see where the time is spent in the "Normal, Low Resolution" mode:

This looks very similar to the 10.8, non-retina rendering, though some function names have changed. There is the familiar img_colormatch_read/CGColorTransformConvertData call which is eating a good chunk of CPU. The ripc_RenderImage/ripd_Mark/argb32_image stack is similar to 10.8, and reasonable in CPU cycles consumed.

Looking at the Low Resolution mode, it really does behave similar to that of 10.8 (though it's depressing to see that it still takes as long to run on an i7 as 10.8 did on a C2D, hmm). Let's look at the full-resolution Retina mode:

img_colormatch_read is present once again, but what's new is that ripc_RenderImage/ripd_Mark/argb32_image have a new implementation, calling argb32_image_mark_RGB24 -- and argb32_image_mark_RGB24 is a beast! It uses more CPU than just about anything else. What is going on there?

Conclusions
If you ever feel as if modern OSX versions have gotten slower when it comes to updating the screen, you would be right. The basic method of drawing ixels rendered in a platform-independent fashion to screen has gotten significantly slower since Snow Leopard, most likely in the name of color-accuracy. In my opinion this is an oversight on Apple's part, and they should extend the CoreGraphics APIs to allow manual application of color correction.

Additionally, I'm suspicious that something odd is going on within the function argb32_image_mark_RGB24, which appears to only be used on Retina displays, and that the performance of that function should be evaluated. Improving the efficiency of that function would have a positive impact on the performance of many third party applications (including REAPER).

If anybody has an interest in duplicating these results or doing further testing, I have pushed the updates to the LICE test application to our WDL git repository (see WDL/lice/test/).

Update: July 3, 2014
After some more work, I've managed to get the CPU use down to a respectable level in non-Retina mode (10.8 on the iMac, 10.9/Low Resolution on the Retina MBP), by using the system monitor's colorspace:

Using this colorspace with CGContextCreateImage prevents CGContextDrawImage from calling img_colormatch_read/CGColorTransformConvertData/etc. On the C2D 10.8, it gets it down to 1-2ms per frame, which is reasonable.

However, this mode is appears to be slower on the Retina MBP in high resolution mode, as it calls argb32_image_mark_RGB32 instead of argb32_image_mark_RGB24 (presumably operating on my buffer directly rather than the intermediate colorspace-converted buffer), which is even slower.

Update: July 3, 2014, laterOK, if you provide a bitmap that is twice the size of the drawing rect, you can avoid argb32_image_mark_RGBXX, and get the Retina display to update in about 5-7ms, which is a good improvement (but by no means impressive, given how powerful this machine is). I made a very simple software scaler (that turns each pixel into 4), and it uses very little CPU. So this is acceptable as a workaround (though Apple should really optimize their implementation). We're at least around 6ms, which is way better than 12-14ms (or 29ms which is where we were last week!), but there's no reason this can't be faster.Update (2017): the mentioned method was only "faster" because it triggered multiprocessing, see this new post for more information.

As a nice side effect, I'm adding SWELL_IsRetinaDC(), so we can start making some things Retina aware -- JSFX GUIs would be a good place to start...

midi2osc, as mentioned in the last post, got some updates which made its name obsolete, particularly the ability to send MIDI and receive OSC, so it has now been renamed OSCII-bot. Other mildly interesting updates:

OSX version

Can load multiple scripts, which run independently but can share hardware

match() and oscmatch(), which can be used for simple regular expressions with the ability to extract values

Ability to detect stale devices and reopen them

Scripts can output text to the newly resizeable console, including basic terminal emualtion (\r, and \33[2J for clear)

Vastly improved icon

I'll probably get around to putting it on cockos.com soon enough, but for now a new build is here. Read the readme.txt before using for instructions.

The thing I'm most excited about, in this, is the creation of eel_strings.h, which is a framework for extending EEL2 (the scripting engine that powers JSFX, for one) to add string support. Adding support for strings to JSFX will be pretty straightforward, so we'll likely be doing that in the next few weeks. Fun stuff. Very few things are as satisfying as making fun programming languages to use...

Making installers and web pages is too much of a pain for a small project, so:

Here's another project, this one took less than 24 hours to make. It's a little win32 program called "midi2osc" (license: GPL, binary included, code requires WDL to compile), and it simply listens to any number of MIDI devices, and broadcasts to any number of destinations via OSC-over-UDP.

MIDI and OSC use completely different types of encoding -- MIDI consists of 1-3 byte sequences (excluding sysex), and OSC is encoded as a string and any number of values (strings, floats, integers, whatever). It would be very easy to make a simplistic conversion of every MIDI event, such as 90 53 7f being converted to "/note/on/53" with an integer value of 7f, and so on. This would be useful, but also might be somewhat limited.

In order to make this as useful as possible, I made it use EEL2 to enable user scripting of events. EEL2 is a fast scripting engine designed for floating point computation, that was originally developed as part of Nullsoft AVS, and evolved as part of our Jesusonic/JSFX code. EEL2 compiles extremely quickly to native code, and can have context that is used by code running in multiple threads simultaneously.

For this project the EEL2 syntax was extended slightly, via the use of a preprocessor, so that you can specify format strings for OSC. For example, you can tell REAPER to set a track's volume via:

Internally, { xyz } is stored to a string table and inserted as a magic number which refers to that string table entry. It is cheap, but it works.

Other than that pretty much everything else was a matter of copying and pasting some tedious bits (win32 MIDI device input, OSC message construction and bundling) and writing small bits of glue.

Since writing this, I've found myself fixing a lot of small OSC issues in REAPER. I always tell people how using the thing you make is very important -- I should update that to include the necessity of having good test environments (plural).

Why did I make this? My Zoom R24. This is a great device, but the Windows 7/64 driver has some issues. Particularly:

If the MIDI input device of the R24 is not opened, audio playback is not reliable. This includes when listening to Winamp or watching YouTube. So basically, for this thing to be useful, I need something to keep hitting the MIDI device constantly. So for you Zoom R24 win64 users who have this problem, midi2osc might be able to fix your problems.

If REAPER crashes or is otherwise debugged with the MIDI device open, the process hangs and it's a pain to continue. Moving the MIDI control to a separate process that can run in the system tray = win.

Today I wrote a proof of concept program called "mikmod2rpp" (requires libmikmod and WDL). Most of the code in there is based on the Gravis Ultrasound driver for MikMod, but instead of uploading the sample data to a soundcard, it writes it to .wav files, and instead of playing the samples on the soundcard, it writes a REAPER project file (RPP). It is not perfect, does many things wrong, but it's somewhat usable.